This invention relates to a cleaning composition suitable for tabletting and to tablets made from the composition, and in particular to tablets for use in cleaning ceramics and porcelain surfaces such as toilet bowls and cisterns.
The cleaning of the porcelain surfaces of toilets bowls requires cleaning compositions having specific properties. Thus, such cleaning compositions should be capable of removing lime and unwanted stains and loosening dirt from such surfaces. Furthermore, they should have a disinfecting effect.
Cleaning compositions in tablet form have several advantages over liquid and powered cleaning compositions. Thus, because they are compressed and contain no water they are economical for shipping and storage. Furthermore, they facilitate a correct dosing.
WO 99/32592 and the corresponding U.S. Pat. No. 5,895,781 disclose cleaning tablets for the cleaning of ceramic and porcelain surfaces and comprising from about 20 to about 80% by weight of sulfamic acid, from about 0.1 to about 20% by weight of isoascorbic acid for reducing kinetically inert metal coordination complex stains, a non-interfering surfactant system and a complexing system comprising from about 0.01 to about 10% by weight of ethylenediaminetetraacetic acid (EDTA) and from about 5 to about 45% by weight of citric acid.
The cleaning composition may also contain an effervescing agent, the most preferred effervescing agent being an alkali metal bicarbonate such as potassium and sodium bicarbonate.
The biodegradation of EDTA is slow and cleaning compositions containing EDTA are in many countries considered environmentally unacceptable.
DE 32 09 333 A1 discloses floatable cleaning tablets for the cleaning of toilet bowls having the following composition:
40-60% by weight of sulfamic acid
16-30% by weight of sodium carbonate or a mixture of sodium carbonate and sodium bicarbonate
0.05-6% by weight of an anionic and/or non-ionic tenside
10-20% by weight of a tabletting additive
up to 15% weight of a chlorine-releasing disinfectant, and
up to 10% of various additives such as dyes and fragrances.
Investigations of tablets according to DE 32 09 333 A1 have revealed that, although the initial strength of such tablets is high, they loose strength when stored for longer periods such as 4 weeks, and they become soft after storage for about 8 weeks at room temperature.
Furthermore, it has been found that such compositions tend to adhere to the dies and piston surfaces during the tabletting process and make the removal of the tablets from the dies difficult.